Method of filling a compression matrix with pulverulent material



March 2, 1943.

' w. BOLKY METHOD OF FILLING A COMPRESSION MATRIX WITH A PULVERULENT MATERIAL 2 Sheets-Sheet 1 Filed May 27, 1938 m will March 2, 1943. 1 w, BQLK 2,312,997

METHOD OF FILLING A COMPRESSION MATRIX WITH A PULVERULENT MATERIAL Filed May 27, 1958 2 Sfieets-Sheet 2 IIHIH ZaBaZ/k Patented Mar. 2, 1943 UNITED STATES PATENT OFFICE METHOD OF FILLING A COMPRESSION MA- TRIX WITH PULVERULENT MATERIAL Willem' Bulk, Arnhem, Netherlands; vested in the Alien Property Custodian I Application: May 27, 1938, Serial No. 210,540

In the Netherlands-June 16, 1937 3 Claims.

There have already been proposed a method and a device for filling a compression matrix or a similar space with a pulverulent material by hurling this material into the said space with the aid of the centrifugal force.

By means of the said process and device a given density is imparted to the pulverulent material by centrifuging the same in a stationary cylindrical room in which state of density the material is then conveyed to the compression matrix which it is to fill. A device of this character is shown in Patent No. 2,093,028 granted September 14, 1937.

It has, however, been found in practice that with different kinds of pulverulent material when varying the rate of speed at which the material is rotated inside the cylindrical room of the said device, it is only possible to obtain variations of a very limited nature in the degree of density imparted to the same. This practically amounts to the fact that a given pulverulent material will always be conveyed to the compression matrices in the same state of densi y. so that the said matrices will be continually filled with the material in quantities having a constant Weight.

The present invention has for its purpose to render it possible to vary in a simple manner. in accordance with actual. requirements and without appreciable loss of time the quantity by weight of the pulverulent material with which the moulds are to be filled.

For this purpose according to the invention there is provided between the cylindrical room and the filling place of the compression moulds, a cylinder which close to one of its ends is connected with the. outlet opening of the cylindrical room, whereas a compression mould may be connected with the other (open) end of the cylinder in which cylinder there is arranged a reciprocating plunger with adjustable stroke. With the aid of the said plunger the pulverulent material fed into the cylinder is periodically introduced into the compression mould to be filled,

whereas in the cylindrical space in which the plunger is adapted to reciprocate, there will be left a disc-shaped slice of the material to be propelled and compacted by the said plunger,

after' the filled compression mould will have been expelled with its contents by displacement in a direction at right angles to the axis of the said cylinder.

Preferablythe device may be constructed so that the extreme position of the plunger which is adjacent to the outlet of the cylindrical room Fig. 2 is a longitudinal section partly a side elevation of the'second embodiment.

Figure, 3 is a longitudinal section of a mold and a portion of the cylinder.

In both embodiments one end of a cylinder 3 is connected with the outlet opening 1 of the cylindrical room 2 in which the pulverulent material is being compacted. (open) end 4 of the cylinder 3 a holder 5 containing moulds 6 is adapted to be moved in such a way that each time a mould 6 may be placed opposite the open end 4 of the cylinder 3, in order to be filled.

In the cylinder 3 a plunger 1 is adapted to reciprocate. With the embodiment illustrated in Fig. l the plunger 1 is withdrawn from the cylinder 3 by means of a spring 8, which movement is limited by a collar 9 arranged on the plunger 1 contacting with a stop l0 provided in the plunger guiding means II. In order to displace the plunger 1 against the action of the spring the said stud I4 after it has travelled through the distance separating its head surface from the end of the plunger 1, may urge the said plunger into the cylinder 3 until it has attained the desired depth, compressing the contents thereof and partly conveying the same to the compression mould 6 to be filled. The plunger *1, however, can only be pushed into the cylinder 3 so far that after the compression mould 6 has been filled and removed a quantity designated in Fig. 1 as on of the compressed pulverulent material is left inside the cylinder obturating the open end of the said cylinder in such a way that'after the withdrawal of the plunger the space '03 in the cylinder vacated Along the other material fed through the supply opening I. The

quantity of the material which is left each time in the cylinder 3 and consequently the volume '02 of the filling chamber 3 which becomes vacant after the withdrawal of the plunger, is controlled by the adjustment of the pin M with regard to the cross head I2.

The slice of compacted material '02 which is left in the cylinder 3 at the same time produces an air-tight seal for the said cylinder and also limits the volume us, so that if care is also taken that no air is able to enter the said space 03 along the plunger 1, the fresh supply will be hurled into a vacuum, so that on entering the said space it will not meet with any obstacle. It is advisable for the present purpose to give the open end of the cylinder 3 an outwardly diverging shape because this prevents the slice '02 to be drawn into the cylinder 3 by the vacuum created.

In the modified embodiment according to Fig. 2 the plunger is provided with an extension piece IE on which a sleeve I! has been screwed and secured by a locking nut l3. The sleeve [1 is slidable in a central bore of the cross head l2 which movement is limited by a collar l9 provided on one end of the sleeve l1 and the collar 20 provided on the extension piece I 6. When the cross head 12 is moved towards the righthand side of the drawing, the plunger 1 is finally carried along when the said cross head contacts with the collar l9. When the cross head l2 moves back, the plunger 1 is first withdrawn from the cylinder 3 by the action. of the springs 2| applied to a yoke 22 attached upon-the plunger, until the plunger occupies its extreme backward position, afiter which the cross head will move backwards still further stretching the springsZl.

By the adjustment of the screwed-on sleeve H on the plunger extension piece l6 it is predetermined how far the plunger will be pushed each time into the cylinder 3.

With the embodiment according to Fig. 2 also the plunger 1 each time is pushed into the cylinder 3 only so far that a volume ca (which is an adjustable quantity) is left behind inside the cylinder 3, in order to keep the cylinder end 4 sealed after the removal of a filled compression mould 6 and the withdrawal of the plunger I.

By adjusting or varying during the process the length of the plunger stroke, it may be attained in a very simple manner that the pulverulent material which is always fed to the cylinder 3 in a constant state of density, is brought, during the filling of the compression moulds with the said material, to a higher degree of density desired at a given moment thereby adapting the weight of the contents of the compression moulds to the conditions prevailing at a given moment.

The fact that with the aid of the device described above, the compression moulds after the degree of density of the material with which they are being filled has been changed, willvery soon be filled once more with practically equal quantities of the material, will be evident from the following explanation:

Supposing that the compression moulds 6 which are to be filled have a volume '01, that the volume of the stroke of the plunger 1 when adjusted in a given manner, is '03 and that after each stroke of the said plunger 1 there is left in the cylinder 3 a .volume '02 of the material, whereas the pulverulent material introduced into the cylinder 7 3 has a density d, the space volume v1-+vz+va. 75

when the plunger is withdrawn and the cylinder 3 and the compression mould 6 are empty, will be filled with a pulverulent material having a density d.

By the first stroke of the plunger this volume will be reduced to v1+v2, whereby-a density d1 will be created. This density d1 is equal to:

After the backward stroke of the plunger 1 and the exchange of the filled compression mould 6 for an empty one, while the end of the cylinder remains obturated by the material having a volume m and a density d1 which. is left therein, the cylinder portion vacated by the plunger will be supplied with fresh material having a density d, until the volume 123 will be completely filled therewith. There will then be present in the cylinder a volume of material havinga weight of md+v2d1. The said filling by the second stroke of the plunger will be compressed into the volume v1+vz, whereby the density of the material will become:

Continuing in this manner the density of the material with which a compression mould is bedc=d1b +a[1+b] The density 01' the filling of a compression mould after the "n stroke of the plunger will be found to be Now for b there are three possibilities, viz. b 1; b=l; b 1, b 1 being preferred. In this case, with n==infinite, the valuejlib of the Formula A will merge into the limit-value=0 and ail+b+b b"-] will merge into its a limit-value b so that a 1-t= with n=infinite.

It is evident from the result obtained that instead of supposing that the joint volume v1+vz+m originally was quite empty, it might have been supposed just as well that the said space was filled with material of any degree of density. Always the resulting density will be:

with n=infinite.

This fact, however, would not be of any practical value, if the said resulting. density did not occur very soon, so that it still must be proved that the resulting density which will remain practically constant will already be obtained after a few strokes of the plunger 1.

In order to supply the said proof, it will be necessary to start from Formula A and to ascertain in what manner the terms of the second part of the said formula will behave with increasing values for n.

Supposing. on the basis of practical applications that d=0.80, v1=80, v==20 and m=l00, the

following table will hold goodior the Formula A: I

'n dlb' [a l+b+ 4-0- do 1.60 01! 1. 6(1) 0. 32 0. 800 l. 120 0. 064 0. 900 1.024 0. 0128 0.992 1. (D48 0. (D256 0. moon 1. (I) 1.00

which shows that practically after the fourth stroke of the plunger a density which remains very nearly constant is attained for the fillings of the successive compression moulds.

It is finally observed that it is advisable in the practical embodiment of the device, according to the invention to have the internal diameter of the cylinder of the compression moulds 6 to be filled, larger than that of the cylinder 3, in order to make sure that thoe volume of material which each time is left behind in the cylinder 3, is

crumbled up during the filling of the next compression mould and mixed with the fresh charge of material.

I claim:

1. A method of molding pulverulent material comprising projecting pulverulent material having a predetermined density imparted thereto by means of centrifugal force into avreceptacle of fixed volume, expelling a portion of said material from said receptacle into a mold, compressing said material which has been expelled from the receptacle and that which remains in the receptacle and then removing the mold with the material therein while leaving in said receptacle the remainder of said material for the succeeding molding operation.

2. A method of molding pulverulent material comprising projecting pulverulent material having a predetermined density imparted thereto by means of centrifugal force into a receptacle of fixed volume, expelling a portion of said material from said receptacle into a mold, compressing said material which has been expelled from the receptacle and that which remains in the receptacle maintaining a predetermined proportion between the material in the mold and that remaining in the receptacle and then removing the mold with the material therein while leaving in said receptacle the remainder of said material for the succeeding molding operation.

A method of molding pulverulent material comprising projecting pulverulent material having a predetermined density imparted thereto by means of centrifugal force into a receptacle of fixed volume, expelling a portion of said material from said'receptacle into a. mold, compressing said material which has been expelled from 

